Aftercooler bypass means for a locomotive compressed air system

ABSTRACT

Method and apparatus for heating gases cooled by an aftercooler that receives hot gases from a compressor. The method includes the steps of directing at least a portion of said hot gases to means for bypassing the aftercooler, and using the bypass means to direct hot gases to a location that receives cooled gases from the aftercooler. The hot gases are used at the location to heat the cooled gases when ambient temperature is at or below freezing, and are used downstream from the aftercooler when moisture freezes in the aftercooler.

FIELD OF INVENTION

[0001] The invention relates generally to locomotive air compressors andaftercoolers used to substantially reduce the temperature of highpressure air exiting the compressor, and particularly to a means forpreventing downstream freezing of condensate in the high pressure airwhen outside ambient conditions are at or below freezing.

BACKGROUND OF INVENTION

[0002] U.S. Pat. No. 5,106,270 to Goettel et al., and assigned to theassignee of the present invention, shows an integral compressor andaftercooler that is extremely efficient in cooling hot, high pressuredischarge air from a compressor. When the compressor is operating undera heavy duty cycle the air temperature is reduced to within 2° ofambient temperature. If the compressor is running in a start/stop mannerunder a light duty cycle, the temperatures of the heated gases from thecompressor can be reduced to temperatures within 5° of ambient. Withsuch efficiency it is quite possible for moisture contained in theaftercooler or in the discharge air from the aftercooler to freeze whenoperating under freezing conditions.

SUMMARY OF THE INVENTION

[0003] The present invention provides a means to increase airstreamtemperatures flowing from an aftercooler to essentially remove thepossibility of freezing prior to reaching a reservoir of pressurized airor bypass the aftercooler altogether should freezing occur in theaftercooler. The reservoir is typically fitted with a heated drain valvethat removes (drains) condensate from the reservoir. The freezingproblem is solved by bypassing the aftercooler with at least a portionof the hot air issuing from the compressor and directing the hot air toexhaust piping of the aftercooler. If the aftercooler freezes, all hotair is bypassed. In either case, warm air is supplied to the reservoir.

[0004] In one embodiment of the invention, by-pass of the aftercoolercan be effected by a pipe connected between the compressor andaftercooler exhaust. The pipe provides a constant volume of hot,compressed air flow from the compressor to the aftercooler exhaust.

[0005] In another embodiment of the invention, a three-way valve is usedto mix gases exhausting from the high pressure head of the aircompressor and from an aftercooler to provide the warmer airstream. Inboth embodiments, condensate is prevented from freezing in theaftercooler exhaust and thus remains in liquid form long enough to reachthe reservoir and the heated drain valve.

[0006] The three-way valve can be operated by sensing either the mainreservoir inlet temperature or more simply ambient air temperature.Thus, in nonfreezing conditions, the three-way valve directs all highpressure air through the aftercooler so that it can be cooled and anymoisture therein condensed. If, on the other hand ambient temperaturefalls below a certain level, the three-way valve is operated bytemperature sensing means to bypass at least a portion of the highpressure air leaving the compressor.

OBJECTS OF THE INVENTION

[0007] It is, therefore, one of the primary objects of the presentinvention to provide a method and an apparatus to prevent freezing ofcondensate in high pressure air before it reaches a main reservoir in alocomotive and train braking system.

[0008] Another object of the present invention is to provide a methodand an apparatus which provides a constant low volume flow of hotexhaust gases from a compressor directly to aftercooler exhaust piping,the aftercooler being connected to receive the major portion of hotgases from the compressor for cooling.

[0009] Yet another object of the present invention is to provide amethod and an apparatus using a three-way valve that is effective inbypassing an aftercooler when freezing temperatures are sensed.

[0010] In addition to the various objects and advantage of the inventiondescribed above, various additional objects and advantages of theinvention will become more readily apparent to those persons skilled inthe pneumatic art from the following more detailed description of theinvention, particularly, when such description is taken in conjunctionwith the attached drawing Figures and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a diagrammatic side elevation view of a compressorprovided with a pipe for by passing hot gases to an aftercooler exhaust,

[0012]FIG. 2 is a diagrammatic front elevation view of the compressorand by-pass pipe of FIG. 1,

[0013]FIG. 3 is a schematic representation of a three-waythermostatically controlled valve providing a mixing application ofaftercooler and compressor discharge gases,

[0014]FIG. 4 is a sectional view of a three-way valve and thermostat (inelevation) that can be used in the three-way valve of FIG. 3,

[0015]FIG. 5 is a schematic diagram showing a three-way valve operatedby a magnet valve under control of a temperature signal, and

[0016]FIG. 6 shows an embodiment wherein the three-way valve is locatedat the input side of the aftercooler.

BRIEF DESCRIPTION OF A PRESENTLY PREFERRED AND VARIOUS ALTERNATIVEEMBODIMENTS OF THE INVENTION

[0017] Prior to proceeding to the much more detailed description of thepresent invention, it should be noted that identical reference numeralsare used throughout the several views illustrated in the drawing figuresto designate identical components, having identical functions, for thesake of clarity and understanding of the invention.

[0018] Referring now to diagrammatic FIG. 1, an aftercooler 10 is shownconnected to a source of hot high pressure compressed air, such as thehigh pressure cylinder 11 of the multi-cylinder compressor 1, which isshown in the above referenced Goettel et al. patent. In the Goettel etal Patent, hot high pressure air enters an aftercooler to be reduced intemperature for the purpose of condensing water vapor contained in theair to liquid water before the air is used to operate the brakes of arailroad train. As discussed earlier, when operating a compressor andaftercooler in cold temperatures, freezing of water in exhaust piping 12of the aftercooler can take place. Moisture may also freeze in theaftercooler. If the amount of water in the high pressure air issubstantial and freezes, it can block aftercooler tubing and exhaustpiping such that the pressurized air needed for brake operation is notavailable. The aftercooler supplies the reduced temperature, highpressure air to a main reservoir or reservoirs 14, in FIG. 3, on alocomotive where liquid water is drained from the reservoir before thepressurized air is made available for operating the brakes of the train.

[0019] The present invention provides a means to increase airstreamtemperature before reaching reservoir 14 to avoid the freezing problemwhile still reducing substantially the water content in brake air. Thereservoir 14 itself is typically provided with a heated drain (notshown) so that condensate can be removed even under freezing conditions.

[0020] In one embodiment of the invention, air stream temperature inpiping 12 is increased by use of a simple bypass pipe 16 connected tohigh pressure cylinder 11. Pipe 16 bypasses aftercooler 10 to outletfitting and pipe 12 such that a portion of hot gases from cylinder 11are directed to the fitting and pipe 12, the amount of hot gasesby-passed depending on the internal size of the pipe. The major portionof the hot gases are sent directly to aftercooler 10, via a pipe 18 inFIG. 2, for cooling. Pipe 18 is position to close port 23 so that valve22 receives only aftercooler gases through valve port 25 for transfer topipe 12 and reservoir 14.

[0021] Valve 22 can operate in a variable manner by use of a thermostat18 (FIG. 4) located in the valve 22, i.e., the amount of mixing in thevalve 22 to maintain an appropriate temperature in pipe 12 can be madedirectly proportional to ambient temperature. Thus, the colder thetemperature outside the valve 22 the more the thermostat closes to theaftercooler to allow more hot air to mix with the aftercooler exhaustpipe 12. In FIG. 6, hot air flow from compressor 1, enters valve 22 viapipe 24, and flows through a small opening 23A in the valve 22 whenambient temperature falls toward freezing (and below). From opening 23A,air flows through a cylinder 28A of thermostat 28 to exhaust pipe 12.When ambient temperature is above freezing, cylinder 28A closes offopening 23A.

[0022]FIG. 5 of the drawings shows an embodiment of the invention inwhich valve 22 can be operated externally by use of a magnet valve 30pneumatically connected to, valve 22 by a pipe 31. Magnet valve 30 iselectrically operated by a switch 32 connected to a valve operatingmagnet 34. Valve 30 is connected to receive air pressure from the sourceof the hot compressed air via a pipe 36 which the magnet valve 30 usesas control air to operate three-way valve 22. When switch 32 receives afreezing temperature signal or a close to freezing signal, the switch 32closes to apply an appropriate voltage to magnet 34. Magnet 34 isenergized to operate magnet valve 30 in a manner that applies the airpressure received from the source of hot compressed air to three-wayvalve 22 to open the same to the hot gases in pipe 36. Hot gases thusjoin with the cooled gases that enter three-way valve 22 to heat thesame. When ambient temperature rises above freezing, switch 32 is openedto deenergize magnet 34 and valve 30 so that three-way valve 22 returnsto a condition that closes the three-way valve 22 to the hot gasesthereby allowing only cooled gas flow to reservoir 14.

[0023] Switch 32 can be operated by temperature signals originating at alocation remote from the switch 32. Locomotives generate and usetemperature measurements for a variety of reasons. The measurements areusually converted to digital signals for use by computers located in thecabs of locomotives. Switch 32 can be operated by such a digital signalto effect the operation of valve 30.

[0024] In another embodiment of the invention (FIG. 6) three-way valve22 can be located on the “entry” side of aftercooler 10. Again, valve 22can be operated in the manners described above to bypass aftercooler 10and thereby prevent freezing of condensate in pipe 12 when ambientconditions are freezing, and restoring the aftercooler to receive thefull output of hot gases from a source of hot gases when ambient risesabove freezing.

[0025] While the presently preferred embodiment for carrying out theinstant invention have been set forth in detail above, those personsskilled in the brake control art to which this invention pertains willrecognize various alternative ways of practicing the invention withoutdeparting from the spirit and scope of the claims appended hereto.

What is claimed is:
 1. A method of heating gases cooled by anaftercooler receiving hot gases from a compressor, the method comprisingthe steps of: (a) directing a portion of said hot gases to a bypassmeans for by-passing the aftercooler, (b) using said bypass means todirect hot gases to a location receiving cooled gases exhausted from theaftercooler for use at a location downstream from the aftercooler, and(c) using said hot gases bypassed by the bypass means to heat the cooledgases exhausted from the aftercooler.
 2. The method of claim 1 whereinstep (a) includes the step of using a pipe as said bypass means tobypass the aftercooler.
 3. The method of claim 1 wherein step (b)includes the step of using said bypass means to mix hot gases from thecompressor with cooled gases from the aftercooler.
 4. The method ofclaim 3 wherein step (b) includes using a three-way valve as said bypassmeans for gas mixing and by-passing the aftercooler.
 5. The method ofclaim 4 wherein step (b) includes using a temperature sensitive deviceto operate said three-way valve in response to ambient temperatureconditions.
 6. Apparatus for heating gases cooled in an aftercoolerconnected to receive hot gases from a compressor, the apparatuscomprising: means connected to receive a portion of such hot gases fromsuch compressor for directing said portion of said hot gases around suchaftercooler and to a predetermined location receiving cooled gases fromsuch aftercooler, while a remainder of such hot gases is sent to suchaftercooler from such compressor for cooling, such hot gases beingeffective to heat such cooled gases at such receiving location.
 7. Theapparatus of claim 6 wherein said means for bypassing such aftercooleris a pipe connected to and between such compressor and such locationreceiving such cooled gases.
 8. The apparatus of claim 7 wherein saidapparatus further includes a preset safety valve connected to suchcompressor, with an internal size of said pipe being such that uponblockage of such aftercooler due to freezing of moisture in suchaftercooler, said pipe will pass hot gases to such location ordinarilyreceiving cooled gases from such aftercooler in an amount sufficient toprevent said safety valve from operating.
 9. The apparatus of claim 6wherein said means for by-passing such aftercooler includes a three-wayvalve having two ports connected respectively to receive hot gases fromsuch compressor and cooled gases from such aftercooler, and an outletport for directing a mixture of such gases from said valve.
 10. Theapparatus of claim 6 wherein said apparatus further includes atemperature sensitive means for controlling an amount of hot gasesby-passed around such aftercooler and to such location for receivingcooled gases from such aftercooler.
 11. The apparatus of claim 10wherein said temperature sensitive means is a thermostat located in athree-way valve connected to receive both hot and cooled gases.
 12. Theapparatus of claim 10 wherein said temperature sensitive means includesan electrical switch connected to receive a temperature representingsignal.
 13. The apparatus of claim 12 wherein a magnet valve isconnected to receive hot gases from such compressor for operating saidmeans for bypassing such aftercooler, with said electrical switch beingconnected to said magnet valve for operating said magnet valve inresponse to receipt of a temperature representing signal.
 14. Theapparatus of claim 7 wherein said pipe connected to receive hot gasesfrom such source of hot gases and to direct same to a location forreceiving cooled gases from such aftercooler, communicates such hotgases in an amount effective to heat such cooled gases exhausting fromsuch aftercooler, and to bypass completely such aftercooler if moisturefreezes in such aftercooler.
 15. The apparatus of claim 9 wherein saidthree-way valve supplies a mixture of such gases to an output pipe whenambient temperature falls to or close to freezing.
 16. The apparatus ofclaim 15 wherein said three way valve includes a thermostat forcontrolling flow of compressed gases to maintain a temperature of suchmixture of such gases flowing to a reservoir.
 17. The apparatus-of claimis wherein said apparatus further includes a magnet valve connected toreceive hot compressed gases from such source of such gases, and usesame as a control gas for operating said three-way valve.
 18. Theapparatus of claim 17 wherein said apparatus further includes switchelectrically connected to a magnet of said magnet valve, said switchbeing effective to control energization and deenergization of saidmagnet based upon temperature signals received by said switchrepresenting ambient, freezing and above freezing temperatures.
 19. Amethod of by passing an aftercooler connected to receive hightemperature compressed air from a source of such air, the methodcomprising the steps of: (a) connecting (1) a first port of a three-wayvalve to such source of high temperature air, (2) a second port of suchvalve to such aftercooler, and (3) a third port of such valve to anoutput pipe, and (b) opening said valve between said first and secondports to conduct high temperature air through said valve to said thirdport when ambient temperature is near, at or below freezing, and toclose said valve when ambient temperature is above freezing.
 20. Themethod of claim 19 wherein said method include the additional step ofusing a magnet valve to provide control air for said three-way valve foroperating said three way valve in response to changes in ambienttemperature.
 21. The method of claim 19 wherein said method includes theadditional step of using a thermostat located in said three-way valve toopen and close said valve.
 22. The method of claim 20 wherein saidmethod include the additional step of using a switch to energize saidmagnet valve when said switch receives a temperature signal representingan ambient freezing condition.